Wiring timer switch into 2-gang switch setup with common load (red) with downstream load

Question

I want to install a timer switch (it has five wires, red (load), black (hot), white (common), green (ground) and yellow (three-way switching but not needed for my application) to replace one switch in a 2-gang switch box having six incoming romex connections (see first photo). One switch turns on outside lights, and it is this switch I want to replace with the timer. The other switch turns on inside lights and I want it to remain in the circuit. Both loads are on the same circuit - all grounds coming into the box are twisted together and all whites terminate in the same wire nut. There are additional downstream loads (interior lights and fans in a different room) which rely on the junction box connections but have their own downstream switches (this is the source of my confusion).

In the 2-gang junction box, the red (load) wire was shared between both switches (see second photo) - it was a single wire stripped in the middle and wrapped around the screw of the second switch then went on to a wire nut with two black wires I found go out to the respective switched loads - you can see this in photo 2. I hooked up the timer as set out in the instructions, but the downstream lights did not work at all and the timer switch did not switch the intended load (outside lights) which just stayed off.

Any help would be appreciated.

Answer 1

Don't pay attention to the colors

The red wire going to the existing switches in your box is actually a pigtail from the hot feed coming in (the junction of the two blacks), while the two black wires from the switches are the switched feeds going back out.

So, nut the black hot wire from the timer to the existing junction of always-hots that you've pulled out and a pigtail to provide always-hot to the other switch, while the appropriate black switched wire gets nutted to the red wire from the timer. The timer neutral goes to the neutral junction (white wires) that you've pulled out, and the timer ground goes in with the rest of the grounds (which need an actual wirenut on them FYI). Finally, the yellow 3-way wire can stay nutted/tape-insulated off as you don't need it, as you have already indicated.

Answer 2

The black wires on your switches as pictured are actually the switched-hot wires to the lamps. I would tag those with red and blue tape, respectively, if I could access the other end of the wire and also tag it.

The red wires in the photo are simply pigtails. The red color means nothing, the guy was just using a scrap of wire he had left over. They are legal being red, but they'd be more understandable if they were black since they are always-hot. There is a serious - and needless - defect with the red wires, in that two are stacked on a single screw. The pigtail off the right switch should simply go straight to the wire-nut with the blacks and other red. I would replace those red wires with black, or mark them with black tape.

Now that you have the existing wires straight (and marked if you so choose), it should be short work to install the new switch. Just match up the colors.